You may be tempted to use your personal phone number and email to start off with. Don’t this will leave you open to hassles in the future and blurs the lines between your personal life and business.
I advise that you get a dedicated number for your practice so that you can ensure that business calls are routed to that number only. This will allow you to set up tools like WhatsApp Business if you are using a mobile number.
with POPIA you need to make sure that your emails are secure and that you have end to end encryption.
One option is to use a service provider that will assist you with your website hosting as this will include email hosting. The other option is to set up something like Google Workspace as this is secure and you will have access to their full suite of services.